Press and release the "On" key (column 1, row 10) on your TI-84's keypad to turn on your calculator.
Press and release the "2nd" key (column 1, row 2, yellow or orange key). Press and release the "VARS" key (column 4, row 4) to display the "distribution" menu on the TI-84's screen.
Press and release the "3" key (column 3, row 9) to select and display the "invNorm" function.
Use an area of 0.9 for the area parameter that the invNorm function requires. Press and release the "period" key (column 3, row 10). Press and release the "9" key (column 4, row 7). Check that you have typed in the correct number sequence and that the display now reads "invNorm(0.9".
Press and release the "Enter" key (column 5, row 10) to display the z-score for the area to the left of 0.9. Check that the z-score calculated and displayed on the TI-84 screen is "1.28."